I work for an American company, in the US. We have a large branch in Japan.
What is the etiquette with name usage in written communication, with fellow employees I don't know (don't work with normally)? I'm not Japanese but am familiar with the culture, and it feels extremely weird for me to use their first name.
e.g. for 'Hajime (first name) Saito (surname)' do I use:
From working at a western branch of a Japanese owned multinational company, where a lot of our business is with our Japanese colleagues:
The most common, and safest, way to address the Japanese colleagues is simply Surname-san.
The exception would be those that you work with regularly, where they might signal a different title to use, via their email signature (the same as in the west). If you notice they repeatedly sign off with something like "Sincerely, (Firstname)" - then you are generally safe to just use that.
With that said though, do remember that your Japanese colleagues will be used to working with the west - or at least sympathetic to the fact the west uses different forms of address. If you get it wrong, they will almost always be understanding - it's not an area to stress over too much.
It depends on the language you are writing in. If you are writing in English, Mr Saito. If you are writing in Japanese, use -san. If you are not sure of the kanji, you should use katakana.
This is from my time working in a Japanese distribution company here in the UK.
Having worked and lived in Japan myself, I've found that Japanese people who work with Americans are very lenient in terms of understanding American culture. If you address a Japanese person the same way as you would address an American, it's unlikely to cause a lot of unnecessary friction. It might come off as weird to them, but it's unlikely to cause a fuss (plus Japanese people in general are very confrontation-averse so it's not likely to get back to you even if it is a problem).
But the safest way, if you wanted to, would be Surname-san, in this case Saito-san. This form is very impersonal though, so it depends on how personal you want to be; if your work culture encourages informality and camaraderie, you may come across as not a friendly person, so YMMV. If you want to strike a mix of familiarity and respect, First Name-san is also an acceptable form. Not affixing -san is too familiar for your current relationship (although, see above re: Japanese people being lenient towards American cultural norms and being generally confrontation-averse), and Full Name-san is...not a thing.
It's great that you want to learn their way of addressing people, but unnecessary. You're a foreigner no one cares much.
In most languages and cultures it's only 'really' insulting if someone from that language or culture doesn't use the correct address. Because then it is probably on purpose, whereas a foreigner doesn't know better, and doesn't matter much in a cultural sense.
